Weight loss, especially lean body mass, is a major manifestation of HIV infection. Loss of lean body mass (LBM) is the earliest manifestation of the wasting syndrome seen in AIDS patients. Scientific evidence also suggests that a high percentage of deaths is related to malnutrition and wasting. We have recently demonstrated that targeted nutritional intervention using a combination of two amino acids (arginine and glutamine) and a metabolite of leucine, beta-hydroxy-beta-methyl-butyrate (HMB), had marked positive effects in promoting lean body mass, increasing muscle mass and function and improving some essential parameters of immune functions. the proposed study is designed to determine the mechanism(s) by which this amino acid nutrient mixture increased lean body mass and reversed the wasting syndrome in AIDS patients. Ten patients with AIDS who have demonstrated weight loss of 10% or greater in the previous year will be recruited for the study. Patients's diets will be supplemented with the nutrient mixture containing HMB, arginine, and glutamine for 8 weeks. Using stable isotope techniques, whole body protein turnover and muscle protein synthesis and breakdown rates will be assessed prior to and after 8 weeks of supplementation. We hypothesize that the HMB/arginine/glutamine combination will result in an increase in protein synthesis and a decrease in proteolysis leading to a significant reversal in the wasting syndrome seen in these patients, ultimately leading improved longevity and quality of life. PROPOSED COMMERCIAL APPLICATION: This nutritional combination has been shown to enhance immune function and lean mass in wasting AIDS patients. It will be possible to market this combination in a variety of products. A high percent of patients with AIDS will have unintentional weight loss associated with the disease, resulting in a large market potential for the nutritional product. The initial product contains the nutrient combination in a ready-to-drink formulation. A balanced nutritional product containing high quality protein and other nutrients would likely follow. The products will distinguish themselves in the market because they will be based on strong clinical data.